Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a first image in a sequence of a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is a front view of a second image in the sequence; and,

FIG. 3 is a front view of a third image in the sequence.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 through 3. The process or period in which an image transitions to another image forms no part of the claimed design.

The broken line showing of a display screen or portion thereof with transitional graphical user interface is for the purpose of illustrating portions of the article and forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 